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<pre><span class="sourceLineNo">001</span><a name="line.1"></a>
<span class="sourceLineNo">002</span>/*<a name="line.2"></a>
<span class="sourceLineNo">003</span> * Copyright (C) 2011 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<span class="sourceLineNo">004</span> *<a name="line.4"></a>
<span class="sourceLineNo">005</span> * $Id: GraphCloneRegistry.html 740 2013-10-02 21:27:31Z archie.cobbs $<a name="line.5"></a>
<span class="sourceLineNo">006</span> */<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span>package org.dellroad.stuff.java;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>import java.util.ArrayDeque;<a name="line.10"></a>
<span class="sourceLineNo">011</span>import java.util.IdentityHashMap;<a name="line.11"></a>
<span class="sourceLineNo">012</span><a name="line.12"></a>
<span class="sourceLineNo">013</span>/**<a name="line.13"></a>
<span class="sourceLineNo">014</span> * A registry for copies of {@link GraphCloneable} objects used during &lt;i&gt;graph cloning&lt;/i&gt; operations.<a name="line.14"></a>
<span class="sourceLineNo">015</span> * A &lt;i&gt;graph clone&lt;/i&gt; of a graph of objects is a deep copy without duplicates and preserving reference topology.<a name="line.15"></a>
<span class="sourceLineNo">016</span> *<a name="line.16"></a>
<span class="sourceLineNo">017</span> * &lt;p&gt;<a name="line.17"></a>
<span class="sourceLineNo">018</span> * See {@link GraphCloneable} for a complete description.<a name="line.18"></a>
<span class="sourceLineNo">019</span> * &lt;/p&gt;<a name="line.19"></a>
<span class="sourceLineNo">020</span> *<a name="line.20"></a>
<span class="sourceLineNo">021</span> * @see GraphCloneable<a name="line.21"></a>
<span class="sourceLineNo">022</span> */<a name="line.22"></a>
<span class="sourceLineNo">023</span>public class GraphCloneRegistry {<a name="line.23"></a>
<span class="sourceLineNo">024</span><a name="line.24"></a>
<span class="sourceLineNo">025</span>    private final IdentityHashMap&lt;Object, Object&gt; map = new IdentityHashMap&lt;Object, Object&gt;();<a name="line.25"></a>
<span class="sourceLineNo">026</span><a name="line.26"></a>
<span class="sourceLineNo">027</span>    private final ArrayDeque&lt;GraphCloneable&gt; stack = new ArrayDeque&lt;GraphCloneable&gt;();<a name="line.27"></a>
<span class="sourceLineNo">028</span><a name="line.28"></a>
<span class="sourceLineNo">029</span>    /**<a name="line.29"></a>
<span class="sourceLineNo">030</span>     * Get the unique clone of a given value during a graph clone operation, creating it if necessary.<a name="line.30"></a>
<span class="sourceLineNo">031</span>     *<a name="line.31"></a>
<span class="sourceLineNo">032</span>     * &lt;p&gt;<a name="line.32"></a>
<span class="sourceLineNo">033</span>     * If the {@code value} has already been cloned and registered with this instance, it is returned.<a name="line.33"></a>
<span class="sourceLineNo">034</span>     * Otherwise, a new clone of {@code value} is created and registered with this instance by invoking<a name="line.34"></a>
<span class="sourceLineNo">035</span>     * {@link GraphCloneable#createGraphClone value.createGraphClone()}, and then returned.<a name="line.35"></a>
<span class="sourceLineNo">036</span>     * &lt;/p&gt;<a name="line.36"></a>
<span class="sourceLineNo">037</span>     *<a name="line.37"></a>
<span class="sourceLineNo">038</span>     * &lt;p&gt;<a name="line.38"></a>
<span class="sourceLineNo">039</span>     * If the {@code value} is null, null is returned.<a name="line.39"></a>
<span class="sourceLineNo">040</span>     * &lt;p&gt;<a name="line.40"></a>
<span class="sourceLineNo">041</span>     *<a name="line.41"></a>
<span class="sourceLineNo">042</span>     * @param value original value<a name="line.42"></a>
<span class="sourceLineNo">043</span>     * @return unique clone of {@code value}, or null if {@code value} is null<a name="line.43"></a>
<span class="sourceLineNo">044</span>     * @throws IllegalStateException if {@link GraphCloneable#createGraphClone value.createGraphClone()}<a name="line.44"></a>
<span class="sourceLineNo">045</span>     *  fails to invoke {@link #setGraphClone setGraphClone()}<a name="line.45"></a>
<span class="sourceLineNo">046</span>     * @throws IllegalStateException if {@link GraphCloneable#createGraphClone value.createGraphClone()}<a name="line.46"></a>
<span class="sourceLineNo">047</span>     *  invokes {@link #setGraphClone setGraphClone()} more than once<a name="line.47"></a>
<span class="sourceLineNo">048</span>     * @throws IllegalStateException if {@link GraphCloneable#createGraphClone value.createGraphClone()}<a name="line.48"></a>
<span class="sourceLineNo">049</span>     *  fails to invoke {@link #setGraphClone setGraphClone()} prior to recursing on other {@link GraphCloneable} fields<a name="line.49"></a>
<span class="sourceLineNo">050</span>     */<a name="line.50"></a>
<span class="sourceLineNo">051</span>    @SuppressWarnings("unchecked")<a name="line.51"></a>
<span class="sourceLineNo">052</span>    public &lt;T extends GraphCloneable&gt; T getGraphClone(final T value) {<a name="line.52"></a>
<span class="sourceLineNo">053</span><a name="line.53"></a>
<span class="sourceLineNo">054</span>        // Verify parent clone registered itself before recursing on children<a name="line.54"></a>
<span class="sourceLineNo">055</span>        final GraphCloneable parent = this.stack.peekFirst();<a name="line.55"></a>
<span class="sourceLineNo">056</span>        if (parent != null &amp;&amp; !this.map.containsKey(parent))<a name="line.56"></a>
<span class="sourceLineNo">057</span>            throw new IllegalStateException("must invoke setGraphClone() prior to recursing via getGraphClone()");<a name="line.57"></a>
<span class="sourceLineNo">058</span><a name="line.58"></a>
<span class="sourceLineNo">059</span>        // Handle null<a name="line.59"></a>
<span class="sourceLineNo">060</span>        if (value == null)<a name="line.60"></a>
<span class="sourceLineNo">061</span>            return null;<a name="line.61"></a>
<span class="sourceLineNo">062</span><a name="line.62"></a>
<span class="sourceLineNo">063</span>        // Have we already cloned the value?<a name="line.63"></a>
<span class="sourceLineNo">064</span>        if (this.map.containsKey(value))<a name="line.64"></a>
<span class="sourceLineNo">065</span>            return (T)this.map.get(value);<a name="line.65"></a>
<span class="sourceLineNo">066</span><a name="line.66"></a>
<span class="sourceLineNo">067</span>        // Need to recurse<a name="line.67"></a>
<span class="sourceLineNo">068</span>        this.stack.addFirst(value);<a name="line.68"></a>
<span class="sourceLineNo">069</span>        try {<a name="line.69"></a>
<span class="sourceLineNo">070</span><a name="line.70"></a>
<span class="sourceLineNo">071</span>            // Create new clone<a name="line.71"></a>
<span class="sourceLineNo">072</span>            try {<a name="line.72"></a>
<span class="sourceLineNo">073</span>                value.createGraphClone(this);<a name="line.73"></a>
<span class="sourceLineNo">074</span>            } catch (CloneNotSupportedException e) {<a name="line.74"></a>
<span class="sourceLineNo">075</span>                throw new RuntimeException(e);<a name="line.75"></a>
<span class="sourceLineNo">076</span>            }<a name="line.76"></a>
<span class="sourceLineNo">077</span><a name="line.77"></a>
<span class="sourceLineNo">078</span>            // Verify it was registered<a name="line.78"></a>
<span class="sourceLineNo">079</span>            if (!this.map.containsKey(value))<a name="line.79"></a>
<span class="sourceLineNo">080</span>                throw new IllegalStateException("createGraphClone() failed to invoke setGraphClone() for value " + value);<a name="line.80"></a>
<span class="sourceLineNo">081</span><a name="line.81"></a>
<span class="sourceLineNo">082</span>            // Return clone<a name="line.82"></a>
<span class="sourceLineNo">083</span>            return (T)this.map.get(value);<a name="line.83"></a>
<span class="sourceLineNo">084</span>        } finally {<a name="line.84"></a>
<span class="sourceLineNo">085</span>            this.stack.removeFirst();<a name="line.85"></a>
<span class="sourceLineNo">086</span>        }<a name="line.86"></a>
<span class="sourceLineNo">087</span>    }<a name="line.87"></a>
<span class="sourceLineNo">088</span><a name="line.88"></a>
<span class="sourceLineNo">089</span>    /**<a name="line.89"></a>
<span class="sourceLineNo">090</span>     * Register the given clone as the unique instance associated with the object currently being cloned.<a name="line.90"></a>
<span class="sourceLineNo">091</span>     *<a name="line.91"></a>
<span class="sourceLineNo">092</span>     * &lt;p&gt;<a name="line.92"></a>
<span class="sourceLineNo">093</span>     * The "object currently being cloned" is the {@link GraphCloneable} object associated with the top-most invocation<a name="line.93"></a>
<span class="sourceLineNo">094</span>     * of {@link GraphCloneable#createGraphClone GraphCloneable.createGraphClone()} on the Java execution stack.<a name="line.94"></a>
<span class="sourceLineNo">095</span>     * &lt;/p&gt;<a name="line.95"></a>
<span class="sourceLineNo">096</span>     *<a name="line.96"></a>
<span class="sourceLineNo">097</span>     * &lt;p&gt;<a name="line.97"></a>
<span class="sourceLineNo">098</span>     * This method should only be invoked within implementations of<a name="line.98"></a>
<span class="sourceLineNo">099</span>     * {@link GraphCloneable#createGraphClone GraphCloneable.createGraphClone()}.<a name="line.99"></a>
<span class="sourceLineNo">100</span>     * &lt;/p&gt;<a name="line.100"></a>
<span class="sourceLineNo">101</span>     *<a name="line.101"></a>
<span class="sourceLineNo">102</span>     * @param clone the clone associated with the current object being graph cloned; may be null (but that would be weird)<a name="line.102"></a>
<span class="sourceLineNo">103</span>     * @throws IllegalStateException if the current thread is not executing within<a name="line.103"></a>
<span class="sourceLineNo">104</span>     *  an invocation of {@link GraphCloneable#createGraphClone GraphCloneable.createGraphClone()}<a name="line.104"></a>
<span class="sourceLineNo">105</span>     */<a name="line.105"></a>
<span class="sourceLineNo">106</span>    public void setGraphClone(GraphCloneable clone) {<a name="line.106"></a>
<span class="sourceLineNo">107</span><a name="line.107"></a>
<span class="sourceLineNo">108</span>        // Sanity check<a name="line.108"></a>
<span class="sourceLineNo">109</span>        final GraphCloneable current = this.stack.peekFirst();<a name="line.109"></a>
<span class="sourceLineNo">110</span>        if (current == null)<a name="line.110"></a>
<span class="sourceLineNo">111</span>            throw new IllegalStateException("not executing within an invocation of GraphCloneable.createGraphClone()");<a name="line.111"></a>
<span class="sourceLineNo">112</span>        if (this.map.containsKey(current))<a name="line.112"></a>
<span class="sourceLineNo">113</span>            throw new IllegalStateException("duplicate invocation of setGraphClone()");<a name="line.113"></a>
<span class="sourceLineNo">114</span><a name="line.114"></a>
<span class="sourceLineNo">115</span>        // Register clone<a name="line.115"></a>
<span class="sourceLineNo">116</span>        this.map.put(current, clone);<a name="line.116"></a>
<span class="sourceLineNo">117</span>    }<a name="line.117"></a>
<span class="sourceLineNo">118</span>}<a name="line.118"></a>
<span class="sourceLineNo">119</span><a name="line.119"></a>




























































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